Electric Pre-Rotator

wolfy

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Well done so far mate will be interesting to see the results, I can't remember if you said already but what Rrpm are you expecting and what size rotor and how many watts is your motor?

wolfy
 

wolfy

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That video was 3 years ago. At that time I used a knob for control. Now I have 3 buttons and a micro controller. off/reset, Idle, where it takes it from a few RPM to idle speed of 65 RRPM, and fly, taking it from idle to full RRPM. I've seen 215 RRPM peak but it pulls past that. I use between 375-500 milliamp hours for a complete spin up. idle, taxi at idle, and full prerotation, so, between 6 and 10 full prerotations for the batteries I use. I'm working with Denis at Gyrotechnic to fit it to his rotorhead. After I do that I'll work on fitting it to existing Wunderlich heads.
Hi John could you share anymore info on your set up,
2300w?
How many Kv?
What is your total reduction ratio from motor to rotor?
Rotor diameter?
Currently designing and just comparing notes.

thanks wolfy
 

Sv.grainne

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You provided specs on the motor, 2000W 40-60 Amps / 12-48V DC 4.5 HP, but wondering what voltage you are using for your test setup? How long from a dead stop to suitable rotor speed??

Bobby
 

jm-urbani

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It does kind of look one of those exploding devices.....and the batteries are lithium ion after all.... not thrilled about that but Kolbalt is using the best quality batteries...Panasonic 18650's.
hooo yes your right ... I will be charging the lipos today .. and do the wiring
 

wolfy

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I have just found a few more motor suppliers, some very powerful motors.
Alien power systems.com
Freerchobby.com

I am still trying to get my head around Kv values, I understand that a lower kv will mean higher torque at a lower speed.
But in our situation we are trying to get to a given rrpm, so a lower kv motor will need less reduction to the Bendix than a higher kv motor meaning the torque applied to the Bendix will be the same.
So for our application is the Kv value of any real importance, given that the total reduction will be adjusted to suit target rrpm?
Meaning that the kw value is really the only one of use?

wolfy
 

XXavier

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I have just found a few more motor suppliers, some very powerful motors.
Alien power systems.com
Freerchobby.com

I am still trying to get my head around Kv values, I understand that a lower kv will mean higher torque at a lower speed.
But in our situation we are trying to get to a given rrpm, so a lower kv motor will need less reduction to the Bendix than a higher kv motor meaning the torque applied to the Bendix will be the same.
So for our application is the Kv value of any real importance, given that the total reduction will be adjusted to suit target rrpm?
Meaning that the kw value is really the only one of use?

wolfy

I'm trying to follow the discussion...

What do you mean with 'Kv'...?
 

wolfy

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It means rpm per volt applied, so a 150Kv motor will do 1500rpm from 10 volts. It is also a kind of torque constant in laymen terms.

wolfy
 

Sv.grainne

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i guess i don't understand your questions. I tested the motor and controllers from 12v up to 40 volts to be sure everything was working good as configured and i have not tested ah draw on the batteries since i haven't tested what it will do with rotors being spun up. if it does that effectively that's all i care about. I will worry about capacity after it spools up my rotors to 200 rrpm or not. As far as conditions go not sure what you mean....weather, temps, calm winds?
My question was what voltage and current did you test at? How many rotor spinups do you estimate on your battery bank before requiring a recharge? Will you be able to recharge on craft or require external power source?

Bobby
 

XXavier

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A question from an outsider...

Wouldn't it be possible to use supercapacitors in place of batteries? They might be lighter. And it wouldn't matter if they were completely discharged with the pre-rotation, since they could be recharged afterwards, once in flight...
 

jm-urbani

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A question from an outsider...

Wouldn't it be possible to use supercapacitors in place of batteries? They might be lighter. And it wouldn't matter if they were completely discharged with the pre-rotation, since they could be recharged afterwards, once in flight...
Hi Xavier,
Thorically supercapacitors have a 10W/hour capacity per kilo, if you need 6000W during one minute (pre-spinning time), so you would need a a 100Wh supercapacitor pack to pre-spinn one minute at 6000w, and the pack would weight 10 kilos
but the module I saw on ebay gives rather 18Wh for 5 kilos ... .. and cost 400 euro each ... (see the document below)
so to get 100 Wh you would need 2.5 packs... so 27.5 kilos ..
I hope I did not do the maths properly and that I am wrong ... if I am correct supercapacitors are not our solution .
ok you could bet on the fact that 30 seconds would be enough to pre-spinn (possible) but you still would need a 14 kilos pack ...
you could also think that super capacitor can be recharged fastly ... but the rotax 912 generators only outputs 250w .. so in order to get 100wh out of it it would take 24 minutes ... one take off every 24 minutes ..
new super capacitors cells will be better but for the moment I have not found them ... if you find supercondensators available with better energy density let me know ( I did not search for long)

supercapacitor.PNG
 
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XXavier

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You're probably right...

If I proposed the 'supercaps' was only because capacitors can be discharged almost completely in a very short time, need little or no maintenance and have a very long life.

Fully discharging a battery in only one minute will probably damage it...

There's now a lot of interest and innovation in 'supercaps', as they are being used in cars in order to store and re-use braking energy. Hence, in the near future we may expect better and lighter supercaps, more easily available and at a reasonable price...
 

jm-urbani

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Yes ...
I have calculated my pack for 10 pre spins down to 30 % of the battery , it leaves me design errors margins .. even if i get only 6 pre-pins i won’t get in the danger batt zone
Reall tests will be the only judge .
We have to test all we can and super capacitor will better
But now for an amateur it is not yet the time
We have to check the rc command offers, when the super capacitor will work for them they will sell solutions
 
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OuterMarker

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Have there been any discussions about the cause and effect of the weight at the top of the mast with this type of system? Who was it that used a heavy metal coat hanger to absorb the electrical load during a soft start to prevent burning up the electronics?
 

gyrodude

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No idea
There is new battery technology on the horizon. Toyota will be coming out with a vehicle that has a solid state battery setup. There is no fire danger like the lipo and lithium ion batteries. The range will be 600miles or double any other electric vehicle and have a 30 min recharge time. I could drive from NC to Wachula plug it in and recharge and drive home.
 

Jazzenjohn

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Kv is how many rpms the motor will turn per volt, but they are expecting you to have voltages somewhere near the recommended for that to be true. A 1 volt test isn't likely to give you an accurate result for higher voltage motors. I don't believe looking at Kv comparing different manufacturers motors has much to do with a rated torque, although if 2 motors that are otherwise exactly the same but have different Kv's, the lower Kv motor would generally have a bit more low end torque and several other differences like lower max RPM, Lower total power, and lower current capacity. Again, generally.

As far as weight at the top of the mast, unless you are putting several lead acid batteries up there, something i've never seen anyone do, the weight of most electric prerotators are about the same or even lighter than those with bendix's and heavy flex cables.
 

jm-urbani

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There is new battery technology on the horizon. Toyota will be coming out with a vehicle that has a solid state battery setup. There is no fire danger like the lipo and lithium ion batteries. The range will be 600miles or double any other electric vehicle and have a 30 min recharge time. I could drive from NC to Wachula plug it in and recharge and drive home.
I have a Bmw c evolution motor bike and it is true it is limited in range but the range has trippled since my vectrix scooter 11 years back in time
I am pretty confident that the range in ev will better
 

Smack

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Have there been any discussions about the cause and effect of the weight at the top of the mast with this type of system?
I don't have a gyro to test this, but it would seem a simple experiment for someone to add (in small steps?) the equivalent weight to the top of their mast and note the change, if any.
I'm also interested in this answer !
Brian
 

Jazzenjohn

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Few people would say anything if a person swapped their Dragon Wings for Sky Wheels but that is effectively adding 40 pounds or so to the top of your mast. How come no one is the least bit concerned about that? My entire rotorhead including prerotator motor batteries, everything, weighs 10 1/2 pounds. Most electric prerotators are lighter, not heavier, some dramatically lighter.1581967561797.png
 
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